Ionic-liquid-mediated pretreatment and enzymatic saccharification of Prosopis sp. biomass in a consolidated bioprocess for potential bioethanol fuel production

The efficacy of ionic liquid (IL)-based pretreatment of lignocellulosic biomass (LB) can be enhanced by simultaneous application of surfactants/salts/deep eutectic solvent (DES) systems which may realize more effectual biorefining of LB to biofuels or other commodities. However, due to inhibitory nature of IL, IL-stable saccharification enzymes (cellulase/xylanase) are desired for enzymatic hydrolysis of IL-pretreated biomass. Bacillus spp. are considered as the super microbial factories for production of commercially important robust enzymes. The current study presents the enhanced production (1.438-fold) of an IL-stable cellulase from a newly isolated IL-tolerant Bacillus amyloliquefaciens SV29 by statistical optimization using agroindustrial residues as carbon (groundnut shell) and nitrogen source (mustard cake). The process variables such as groundnut shell and mustard cake, incubation time, and inoculum size were optimized. The enzyme preparation (cellulase/xylanase) was evaluated for its saccharification potential of Prosopis sp. (twigs/pods) biomass that was pretreated either with IL (1-ethyl-3-methylimidazolium methanesulfonate, EMIMS) standalone or IL along with surfactants/salts/DES systems in a consolidated bioprocess (CBP), i.e., one pot consolidated bioprocess, due to several technoeconomic advantages of the latter. No reported studies are available on bioconversion of Prosopis sp. biomass using IL or CBP. Sugar yield was enhanced when IL was used along with either DES choline chloride glycerol (54.4%) or with FeSO4 (51%). Thus, the pretreatment efficacy of EMIMS is substantially enhanced when used in combination with choline chloride glycerol or FeSO4 for getting increased sugar yield upon enzymatic hydrolysis of Prosopis sp. biomass with IL-stable enzymes.